Everything Can Be Upgraded

What should I do if I travel to the world of Demon Slayer? Surrounded by a group of younger brothers and sisters who are waiting for food, what can I do? I am also desperate. Not only that, his father in the new world is very sick and about to die. But it doesn't matter. I just want to know why you are so alive when you are about to die of illness? Phew~ Fortunately, I have a golden finger. Congratulations on killing a bug and gaining some experience. Congratulations on killing a chicken and gaining ten experience points. Congratulations on killing a pig and gaining 100 experience points. Spend one hundred experience points, and your constitution LV+1. Spend one thousand experience points and your swordsmanship LV+1. Spending 10,000 experience points, your hollow ring will have a space LV +1. The most important thing is that at the top of my skill list, in the most conspicuous place, there is a golden skill called the power of time and space. It seems to be... This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.